Conventionally, as a cutting insert (hereinafter generally referred to as an “insert”) for use in a face milling process, an insert configured so that major cutting edges 24 and 25 are gradually inclined downward as separating from a corner part has been proposed (for example, refer to Japanese Unexamined Patent Publication No. 11-333616).
However, according to the insert of Japanese Unexamined Patent Publication No. 11-333616, rake surfaces 35 and 36 located correspondingly to the major cutting edges 24 and 25 are flat surface shaped surfaces as shown in FIG. 7 and the like. Therefore, the chips generated by the major cutting edges 24 and 25 are discharged after passing through the flat surface shaped rake surfaces 35 and 36 while following the inclined shape of the major cutting edges 24 and 25. Consequently, the chips are less susceptible to stable curling, and hence the chips may extend long. As a result, there is a risk that surface quality of a target machining surface of a workpiece may be deteriorated due to chip biting between the insert and the workpiece.
Accordingly, there is a demand for an insert that reduces the foregoing chip biting and has excellent chip discharge performance.